The MRI apparatus is an apparatus which measures an NMR signal generated by the object, especially, nuclear spins which form human tissue and images the shapes or functions of the head, abdomen, limbs, and the like in a two-dimensional manner or in a three-dimensional manner. In the imaging, different phase encoding and different frequency encoding are given to NMR signals by the gradient magnetic field, and the NMR signals are measured as time-series data. The measured NMR signals are reconstructed as an image by two-dimensional or three-dimensional Fourier transform.
In the above MRI apparatus, when a moving material or tissue in motion, such as blood, is present in the imaging region, the phase of the spins caused by the movement or motion is reconverged (rephased) without depending on the speed or acceleration of the movement or motion by the pulse sequence in which a rephasing gradient magnetic field based on the GMN method is added, so that the influence (that is, artifacts) on the image quality is eliminated or reduced (hereinafter, this is called a rephasing effect). This rephasing gradient magnetic field is applied in the form of first order or second order in at least one direction of a slice direction, a phase encoding direction, and a frequency encoding direction (for example, PTL 1).